Effect of Surface Passivation and Substrate on Proton Irradiated AlGaN/GaN HEMT Transport Properties

Abstract

In this work, we fabricate Van der Pauw structures on AlGaN/GaN high electron mobility transistors (HEMTs) with both SiN and AlN passivation layers and both SiC and GaN substrates to study temperature dependent electron transport properties of 2 dimensional electron gases (2DEG) in as-fabricated and proton irradiated devices. We confirm that using a GaN substrate or AlN passivation layer enhances the mobility particularly at low temperatures, though this enhancement is greatly reduced upon irradiating the samples with high proton fluences. Our results suggest that the sheet density may be affected by Al diffusion in the sample creating electron donating impurities, which freeze out around 200 K and are more prominent in AlN passivated samples and minimized by using a GaN over a SiC substrate. Additionally, we show that a large dose of radiation forms traps in the AlGaN layer, which drop the sheet density at high proton fluences. GaN, among other wide bandgap semiconductors, is of considerable interest for next-generation energy efficient, high performance devices because their high electron mobility and high breakdown voltage allows them to operate at higher voltages, frequencies, and temperatures than current Si-or GaAs-based devices. One application is the production of AlGaN/GaN high electron mobility transistors (HEMTs) for microwave power amplifiers, making the study of these devices robustness in high energy proton radiation important for potential space applications.

Proton Irradiation of High Aluminum Content AlGaN Polarization Doped Field Effect Transistors

“…The shift from GaAs to GaN led to an approximate improvement of 1000% improvement in radiation resistance. [3][4][5][6][7][8][9] While the bond energy of Ga-As is only 2.17 eV, the bond strength of Ga-N is 9.12 eV. This 4 fold increase in bond strength is not proportionally reflected in the performance improvement, the remainder is likely due to the piezoelectric field at the channel barrier layer interface of AlGaN/GaN reinjecting scattered carriers into the 2DEG.…”

Optimizing performance and yield of vertical GaN diodes using wafer scale optical techniques

“…GaN substrate manufacturing technology, however, is still immature, 4,[6][7][8] and thus heteroepitaxial lateral AlGaN/GaN High Mobility Electron Transistor (HEMT) technology is the industry standard for low voltage devices., Large die sizes are required to produce a breakdown voltage above a kilovolt in lateral GaN devices due to reduced critical field in such device designs 4,5,[9][10][11] . A switch to vertical geometry would increase critical electric field by a factor of 3, improve the breakdown voltage by an order of magnitude, and increase the resistance to radiation damage 4,5,[12][13][14][15] .…”

Alpha Particle Irradiation of High Aluminum Content AlGan Polarization Doped Field Effect Transistors

“…Alpha particle radiation due to its heavier mass presents a larger risk to both electronics and life forms in space than proton irradiation. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] Alpha particle events in GaN High Electron Mobility Transistors (HEMTs) have been studied previously, although not nearly as well as proton irradiation. Danesin et al reported on 2 MeV alpha irradiation and noted a 70% reduction on drain current at a fluence of 10 14 cm −2 .…”